Quarter Knees & Breast Hook:

These are cut from ¼” ply as shown on the plans. There are two ways they can be installed. Cleats can be glued to the inside of the sides such that when glued in place the ply pieces are flush with the gunwales. The top of the gunnels and stem, or gunwales and transom can be planed or sanded flat. The ply pieces are then glued flat on top. The first approach looks tidier to most folks, but the second approach is a bit easier. The edges can be left as is, or a scrap of ¾” solid wood or ¼” ply can be glued to the underside edges for stiffness and appearance sake.

Handle-Braces: Variation on hook and knees. Details and pictures here.

If all of the above seems tricky here is another approach. ¾” to 1" dowels can be as combination braces and handles. 

These lend the stiffness and resistance to both compression and expansion that breast hooks and knees provide while also functioning as handy handles or tie points while car toppng.